Circular radiator air heating furnace with spiral air baffles



Feb. 27, 1951 R. w. RIFLEY CIRCULAR RADIATOR AIR HEATING FURNACE WITHSPIRAL AIR BAFFLES 3 Sheets-Sheet 1 Filed April 12 1948 JNVEN TOR. RayW. EAif/ey ATTORNEYS Feb. 27, 1951 w R|FLEY 2,543,201

CIRCULAR RADIATOR AIR HEATING FURNACE WITH SPIRAL AIR BAFFLES FiledApril 12, 1948 3 Sheets-Sheet 2 INVEN TOR. Ray W Rif/ey aw c/ WATTORNEYS Feb. 27 R. w RlFLEY I CIRCULAR RADIATOR AIR HEATING FURNACEWITH SPIRAL AIR BAFFLES Filed April 12, 1948 3 Sheets-Sheet 3 INVENTOR.y W Rl'fley ATTORNEYS Patented Feb. 27, 1951 CIRCULAR RADIATOR AIRHEATING FUR- NACE WITH SPIRAL A'IR'BAFFLES Ray W. Riiley, Denver,(1010.; Florence Ross Rifley, administratrix of said Ray W. Rifley,deceased, assignor, by mesne assignments, to Florence Ross Rifley,Denver, Colo.

Application April 12, 1948, Serial No. 20,391

13 Claims. (Cl. 126-110) This invention relates to furnaceconstructions, and more particularly to a warm or hot air furnace.

Because of its quick response to changing weather conditions, and thenormally w first cost and cost of installation of auxiliary equipment,such as .air ducts and radiators, the warm or hot air furnace has.achieved wide popularity in many sections of the United States,particularly for use in smaller homes and buildings of one or twostories in height. In a conventional construction, such a furnaceincludes a central combustion chamber, usually disposed vertically, inwhich the fuel is burned. This fuel may be natural or artificial gas,fuel oil or similar petroleum product, or .coal. When coal is utilizedas the fuel, an automatically controlled stoker arrangement is usuallyfound to be more satisfactory than hand firing. In such a furnace construction, the upper end of the combustion chamber is closed, with thehot gases passing laterally through a flue connected to the .combustionchamber at a point adjacent the upper end. ,An air heating space isformed around the combustion chamber by a shell which encloses thecombustion chamber and is spaced laterally therefrom and also at thetop, the space between the top of the combustion chamber and the top ofthe shell forming a plenum or an air mixing and distributing space, theducts for carrying the heated air to the desired points of distributionbeing connected to the plenum. The combustion chamber and shell may, ofcourse, be round, square or rectangular, and with each a plenum ordistributing space at the top. Cool or cold air :to be heated issupplied at one or more points about the periphery of the air heatingspace, adjacent the bottom thereof.

Certain improvements have been made in the construction of warm or hotair furnaces, but these improvements have been directed primarily toincreasing the efliciency of combustion, or improving the path of travelof combustion gases. One such improvement is that of the Lennox furnace,wherein a radiation unit or annular enclosure for the combustion gasesis disposed concentrically and in spaced relation to a cylin- .drical,vertical combustion chamber. The combustion gases, resulting from thecombustion of either gas or oil, pass upwardly in the combustionchamber, then through a short connecting flue at one side to-the annularenclosure, thence around both sides of the annular enclosure, for

exhaust through a flue leading outwardly from the annular enclosure atthe opposite side from the connecting flue. In such construction, theconnecting flue between the combustion cham-- her and the annularenclosure is trapezoidal in cross section, with the narrow end at thetop, to proportion more equally the amount of gases flowing through theannular enclosure. Despite such improvements, there is still room forimprovementin warm and hot air furnaces, occasioned primarily by thetendency toward uneven heating .of the air, and the resultingdifferences in temperature between various parts of the plenum space. Asa result .of such temperature diiferences, one duct may receive agreater amount of air at a considerable different temperature than theair received by other .ducts. Also, when the average temperature of theflue gases is raised, in order that a minimum temperatureof hot airpassing'to the ducts may be produced, the maximum temperature of the airpassing to other ducts may approach a danger point, While the highertemperature of the .flue gases alsomay approach the danger point. Inaddition, the higher the temperature of the flue gases, the less theamount of heat transferred to the air, and

' the lower the efficiency of operation of the furnace.

Among'the objectsof the present invention are toprovide an improvedfurnace of the hot or Warm air type; 'to provide sucha furnace in whicha more even distribution of air to be heated in :the heating spaces isobtained; to provide such a furnace in which the temperature of variousportions of the air being heated are more nearly the same; to providesuch a furnace in which a more uniform temperature of the heated air inthe plenum or distributing space is obtained; toprovidesuch a furnacewherein theflue gas temperature may be reduced without a reduction inthe minimum temperature of the heated air supplied to any single duct;to provide such a furnace which will be more efiicient in operation. andparticularly more efficient in the transfer of heat to the air beingheated; and to provide such a furnace wherein the improvements arerelatively simple and inexpensive.

Other objects and the novel features of this invention will becomeapparent from the description which follows, taken in connection withthe accompanying drawings, in which:

Fig. 1 is a perspective View, with certain parts broken away to show theinterior construction, of a hot air furnace constructed in accordancewith this invention;

Fig. ,2 is a vertical .cross section through the heating portion of thefurnace of Fig. 1;

Fig. 3 is a partial vertical section taken along line 3-3 of Fig. 2;

Fig. 4; is a partial vertical section taken along line 4- of Fig. 2;

Fig. 5 is a horizontal cross section taken along line EI-5 of Fig. 2;and

Fig. 6 is a vertical section similar to Fig. 2, but illustrating analternative embodiment of this invention.

As illustrated in Fig. 1, the principles of this invention may beapplied to a hot air furnace of a type which may operate on either oilor gas as fuel and which includes an outer shell or casing S, into thetop of which an air intake duct or ducts (not shown) delivers air forpassage through a pair of angularly disposed filters ill. The air passesdownwardly to the intake of a blower B, driven in a suitable manner, asby a motor H, the air passing from an air space A within shell S,provided by a partition I2, to casing i3 of the blower B. Rotor i l ofthe blower B forces the air into a heating space H on the opposite sideof the partition l2. Disposed centrally in the heating space H is acombustion chamber 15, in the lower end of which is installed a burnerunit U to which fuel, such as gas, may be supplied through a gas pipe[3. The burner unit U is conventional in construction, the hot gases ofcombustion passing upwardly in the combustion chamber 15, and, as inFig. 2, then at one side to an annular enclosure 11, having verticalinner and outer walls I8 and I8, respectively. The hot gases pass aroundboth sides of the annular enclosure I1 to a flue 19 on the opposite sidethereof, from which the hot gases are exhausted to the stack or chimney.

The heating space H may be substantially rectangular at its lower end,with the upper end formed by a cylindrical shell 20, disposedconcentrically and in spaced relation to the annular enclosure [1. Atransverse partition 21 may extend from the lower end of shell across tothe outer shell S and the partition l2, so as to force the air deliveredby blower B to flow within the confines of shell 20, and upwardlythrough a space 23 between combustion chamber [5 and annular enclosure[1, and also through a space 24 between annular enclosure l1 and theshell 28. The outlet of the blower B may open directly into the heatingspace H, as in Fig. l,

or the blower may be connected by a duct 25, as in Fig. 2, with theheating space H.

In accordance with this invention, in order to force the air flowingupwardly around the combustion chamber to follow a circuitous paththrough the spaces 23 and 24, and preferably such a path that eachportion of the air passes entirely around the combustion chamber, i. e.approximately 360, a plurality of baffles 26, 21, 2 3, 29 and 30,respectively, extend spirally between the exterior of combustion chamberI5 and the inner wall I8 of annular enclosure 11. Similarly, a series ofbaflles 3|, 32, 33, 34 and 35, respectively, extend spirally in space24, between shell 20 and the outer wall [8 of annular enclosure I,1. Asin Figs. 2 and 5, the lower ends of the baflies 25 to inclusive, andalso the baffles 3| to 35, inclusive, are spaced equidistantly, and eachbafile preferably extends for about 360, i. e. makes one completerevolution between the lower end of annular enclosure l1 and the upperend thereof. The baffles 26 to 30, inclusive, and 31 to 35, inclusive,may extend spirally upwardly in the same direction, although thedirection of the battles in space 26 may be the 4 reverse of that of thebafiles in space 23, such as shown in Fig. 6, described in detail later.

In further accordance with this invention, the combustion chamber l5 andthe annular enclosure H are connected by a pair of flues 36 and 31,respectively, flue 33 being a smaller flue disposed in an upperposition, and flue 31 being a larger flue disposed in a lower position.The difference in the size of the flues 36 and 31 tends to equalize theflow of hot gases from combustion chamber [5 to the interior ofenclosure [1, since the hot gases naturally tend to rise and passthrough the upper flue, but the lower flue 31 being larger, causes amore nearly equal proportion of the hot gases to flow to the lowerportion of the annular enclosure l1. As in Fig. 5, the hot gases flowfrom flues 33 and 31 around each side of the annular enclosure l1, asindicated by arrows 38, and thence to stack flue 19.

In further accordance with this invention, the baffles 26 to 30,inclusive, and 31 to 35, inclusive, are so disposed and spaced that oneof the baffles intersects each of the flues I9, 36 and 31, respectively,so that the flues provide a minimum of resistance to flow of air beingheated along the spiral paths provided between the baffles. Thus, as inFigs. 2 and 3, the lower end of bafile 28 is disposed beneath lower flue31, while the next baffle 21 intersects flue 31, preferablysubstantially centrally thereof so that one half of the flue 31 will bein the spiral passageway beneath baffle 21 and the other half in thespiral passageway above baffle 21. Bafiles 28 and 29 are so disposedthat they intersect neither flue 36 nor flue 31, while baffle 33intersects upper flue 36, preferably centrally. Also, the upper end ofbaffle 26, after completing a complete revolution, is disposed aboveflue 3B. As in Figs. 2 and 4, flue I9 is intersected centrally by bafiie34, with baffle 33 passing below and baflie 35 passing above flue l9.Preferably flues I9, 36 and 31 are cylindrical or tubular, for ease inconstruction, although oval, elliptical or other cross-sectional shapesmay be utilized. As is evident from Figs. 2 to 5, inclusive,

each set of baffles is shown as being five in number, but any otherdesired number may be used.

The air passing through the spiral passageway defined by each bafiie andthe next adjacent baffle, preferably passes completely around thecombustion chamber 15 or the annular enclosure l1, so that heat will betransferred on all sides to each portion of the air. This feature is ofimportance in equalizing the transfer of heat to the air, and inmaintaining a more uniform temperature of each portion of the air beingheated, as well as a more uniform temperature of the flue gases. As inFig. 2, each portion of the air being heated, now at or about the sametemperature, passes into the plenum chamber 39 at the top of thefurnace, and thence into duct header 40, from which individual ducts 4|lead to the points of use of the heated air. As will be evident, theswirling movement imparted to the various portions of the air due to themovement thereof through spiral passageways, further tends to increasethe mixing action in plenum chamber 39, thereby insuring a more uniformtemperature of the heated air supplied to the duct header 40.

As indicated previously, sets of baflles may be any desired number, suchas each set of bafiles being four in number, as in Fig. 6. Thus, baffles52 to 45, inclusive, extend spirally in one direction between combus ionchamber [5 and annular enclosure [1, while baffles 46 to 49, inclusive,extend spirally in the opposite direction between the annular enclosure1 l andshell 20. Each baflle again preferably extends for about 360, orone complete revolution. Also, the bafiles intersect the fiues i9, 35and 3?, substantially centrally thereof, as before. Thus, batle 43intersects lower flue 3i, baffle 05 intersects upper flue 36, and baflie49 intersects stack flue l9 centrally. The positions of fines '36 and31' may need to be adjusted slightly upwardly or downwardly, to insurecentral intersection by the respective bafile. The action of the bailies2 to 35, inclusive, and d to '20, inclusive, of Fig. 6, is similar tothat of the babies of the previous embodiment, except that the airpassages may be slightly larger due to the lesser number of battles, anda more thorough mixing of the air in the plenum chamber 30 tends to beproduced, due to the fact that the air discharged from the spacesbetween bailles 02 to 05, inclusive, tends to be moving in the oppositedirection from the air discharged from the spaces between baffles 06 to09, inclusive.

The spiral bafiles may be readily made of sheet metal or other suitablematerial, and may be brazed or otherwise suitably secured to thecombustion chamber, the annular enclosure, or the shell. Since an airtight seal around the edge or each balile is unnecessary, it may in manyinstances be suitable to attach the baffles, as by brazing or the like,only to the inner and outer walls of the annular enclosure, forinstance, so that the enclosure and baffles may, as a unit, be insertedin the furnace. The lines between the combustion chamber and the annularenclosure may be inserted later, or attached to the annular enclosureand baflies, and then attached to the combustion chamber upon assembly.Or, the entire unit may be assembled and the baffles brazed to thecombustion chamber, annular enclosure and shell, in one operation. Theexhaust flue may be inserted, after assembly, through the shell, or maybe made in two sections, one section being attached to the respectivebafile and the annular enclosure, and extending to the outer shell, withthe other section fitting thereinto and. being attached to the firstsection upon assembly.

In controlling the operation of a furnace constructed in accordance withthis invention, substantially conventional control mechanism may beused, but the control may be set so as to increase the effectiveness andefficiency of the furnace operation. In furnace control systemsgenerally in use at the present time, .a thermostat which is responsiveto the temperature in the room or space being heated, is adapted toclose a control circuit whenever the room cools to a predetermined lowertemperature, and to open the circuit whenever the temperature in theroom reaches a predetermined higher temperature. Superimposed upon theroom thermostat control is a circuit controlled by the temperaturewithin the plenum, so that whenever the plenum temperature reaches apredetermined maximum, the burner will be shut oil, and cannot be turnedon again until the plenum cools to a predetermined minimum temperature.The maximum temperature is controlled by the danger of wood or similarmaterial adjacent the furnace or stack catching on fire if the flue gastemperatures are too high, so that a maximum temperature of the fluegases of below 700 F. is necessary, and desirably 500 F. or below.

With a gravity type furnace, i. e. wherein air circulation is bygravity, the controls are normally set higher, since a higher plenumtemperature is necessary to start adequate circulation, so that amaximum of somewhat near 3.00 F. and .a minimum of 225 :F. or above maybe utilized.

In nearly all modern installations, particularly of gas and oil firedfurnaces, a fan or blower is utilized, and the plenum control.temperatures may be lower, while an additional control is usuallyprovided for the fan. The blower control is normally a thermostaticcontrol responsive to the temperature in the plenum, .and is set to turnthe fan on whenever the .plenum temperature is sufiiciently high towarrant, such as 30 F. to 50 F. below the maximum plenum temperature,and toturn the fan off whenever the plenum temperature drops below alower temperature, such as about 30 .F. below the fan startingtemperature. With gravity type furnaces, the stack temperature isgenerally on the order of about twic the plenum temperature, so thatwhen the plenum temperature .reaches a maximum of, say, 300 the stacktemperature will probably be about 600 F., which is approaching thedanger zone, so that it is usual to set the maximum at about 275 F.,roughly equivalent to a stack ternperature of about 550 F., for shuttingoff the fuel.

When a fan or blower is used, the plenum control temperatures may be setsomewhat lower, such as a maximum plenum temperature of 200 F or 210 F.and a minimum of F., with the type of furnace wherein there is a singleheating passage surrounding the combustion chamber, which may be termeda single direct pass furnace. The stack temperature will generally againbe roughly double the plenum temperature, or about 400 F. to 420 butsometimes higher, such as 450 F. to 500 F. The fan control thermostatmay be set to turn the fan on at about 30 F. below the maximum plenumtemperature, or 170 F. to 180 F., and to turn the fan 01f at F. to F.With a type of furnace having an annular enclosure spaced from thecombustion chamber, through which the gases of combustion are alsopassed, which may be termed a double direct pass furnace, the controlsmay be set somewhat lower, such as for .a maximum plenum temperature ofF. and a minimum of 130 F., with the fan starting temperature closer tothe maximum, such as about 150 F. In this type of furnace, the stacktemperatures will be lower, reaching the much safer temperature of about350 F. or slightly less, when the plenum reaches the maximumtemperature. However, there is one common characteristic of the directpass furnace, through which the air is blown by a fan, and this is thatwhen the fan is turned on, the plenum temperature is quickly reduced, sothat the fan then turns on" but the burner stays on and the stacktemperature continually rises, often to as high as 500 F. or more. Thus,when heat is called for by the room thermostat, the burner is turned on,the plenum heats up, then the fan is turned on, then the plenum coolsand the fan turns off, and the later the plenum heats up again and thefan is turned on again, the cycle being repeated until the space to beheated reaches the desired temperature. Not only is such heatingintermittent, but also the continual operation of the burner and thehigher stack temperatures indicate a considerable loss of heat. Theplenum temperature seldom reaches the maximum, but the stack temperaturecontinues high.

In the case of a furnace constructed in accordance with this invention,as indicated by data obtained by tests thereof, a different conditionprevails. The effectiveness and efiioiency of heat transfer to the airis sufficiently greater so that the stack temperature, with the fanrunning, is only slightly greater than the plenum temperature. Forinstance, when the plenum temperature of an experimental model was 225F., the stack temperature was between 230 F. and 240 F. This means thatthe maximum plenum temperature can be set much higher, such as 225 F. to250 F., without danger in the stack. Also, when the fan is turned on,the plenum temperature rises, due to the greater transfer of heat to theair, and as soon as the plenum temperature reaches the maximum, theburner shuts off. As soon as the plenum temperature drops to theminimum, the burner is turned on again. Thus, the fan will runcontinuously, rather than intermittently, thereby continuously supplyingheated air to the space to be heated, and the burner will operateintermittently, the total period of operation thereby being considerablyless, with a consequent saving in fuel. With a higher maximum plenumtemperature, such as 225 F. to 250 F., the minimum plenum temperature isalso preferably set higher, such as about 195 F. to 220 F., to provide a30 F; differential and also to reduce the possibility of condensation inthe stack. The fan control is also preferably set differently inrelation to the plenum control than with a direct pass furnace, the fanbeing set to turn on at a much lower temperature relative to the maximumplenum temperature, such as 190 F., or even lower, and to turn off at atemperature about the same or lower than the temperature at which itturns on, but in any event lower than the minimum plenum temperature,thereby assuring that the fan will continuously supply heated air,which, of course, is the object of using the furnace, and the burnerwill be on a minimum of time.

From the foregoing, it will be apparent that the furnace of thisinvention fulfills to a marked degree the requirements and objectshereinbefore set forth. lhe spiral bafiies in the air heating spacesproduce a more even distribution of air, render the temperature ofvarious portions of the air more nearly the same, and provide a moreuniform temperature of heated air in the plenum or distributing space.More effective heating of the air provides greater efficiency inoperation, and a consequent saving in fuel. The fan will also operatemore nearly continuously, and substantially continuous fan or bloweroperation, as long as heat is called for by the room thermostat, meansthat the space to be heated is heated more quickly and a greater degreeof comfort is assured. Also, there is a possibility of a smaller furnaceand burner requiring less fuel, with consequent obvious savings, forheating a space requiring a larger furnace of the direct pass type. Itwill be evident, of course, that the furnace of this invention may beconstructed in any suitable manner, other than that described; that thespiral baffles of this invention may be applied generally to differentsizes and shapes of air heating spaces; that the number and slope ofbailies may be varied; that other flue arrangements may be used; andthat the control system and its settings may be varied from thatdescribed. It will also be evident that various other changes may bemade, and that embodiments other than those described may exist, allwithout departing from the spirit and scope of this invention.

What is claimed is:

1. In a furnace construction having a generally cylindrical combustionchamber disposed with its longitudinal axis in vertical position, spacedwalls defining an annular enclosure including an inner wall of greaterdiameter and disposed substantially coaxially with and in spaced lateralrelation to said combustion chamber, means for conveying hot gases fromsaid combustion chamber to said annular enclosure, means for permittingsaid gases to exhaust from said annular enclosure, a shell surroundingsaid annular enclosure in spaced relation to the outer wall thereof, andmeans for effecting passage of air to be heated through the spacebetween said combustion chamber and annular enclosure and also throughthe space between said annular enclosure and shell, the improvementwhich comprises a first plurality of spirally extending baffles betweensaid combustion chamber and the inner wall of said annular enclosure;and a second plurality of spirally extending baffles between the outerwall of said annular enclosure and said shell, all of said bafiies beingadapted to cause air to be heated to follow a plurality of circuitouspaths in passing through said spaces.

2. In a furnace construction as defined in claim 1, wherein each baflleextends for about 360.

3. In a furnace construction as defined in claim 1, wherein each bafilehas substantially the same slope and said first and second bafiles areaxially spaced substantially equidistantly.

4. In a furnace construction as defined in claim 1, wherein said firstplurality of bafiies slope in the opposite direction to said secondplurality of baffles.

5. In a furnace construction as defined in claim 1, wherein said firstplurality of baffles slope in the same direction as said secondplurality of baffles.

6. In a furnace construction having a generally cylindrical combustionchamber disposed with its longitudinal axis in vertical position, spacedwalls defining an annular enclosure including an inner wall of greaterdiameter and disposed substantially coaxially with and in spaced lateralrelation to said combustion chamber, a shell surrounding said annularenclosure in spaced relation to the outer wall thereof, an exhaust flueleading from said annular enclosure outwardly through said shell, andmeans for effecting passage of air to be heated through the spacebetween said combustion chamber and annular enclosure and also throughthe space between said annular enclosure and shell, the improvementwhich comprises at least two vertically aligned and spaced fluesconnecting said shell with said annular enclosure on the opposite sideof said enclosure from said exhaust flue; a first plurality of spirallyextending baffles between said combustion chamber and the inner wall ofsaid annular enclosure, said bafi'les being spaced axially so that eachsaid spaced flue will be intersected substantially centrally by abafile; and a second plurality of spirally extending baffles between theouter wall of said annular enclosure and said shell, said bailles beingaxially spaced so that said exhaust flue will be intersectedsubstantially centrally by a baffle.

7. In a furnace construction as defined in claim 6, wherein said upperflue is smaller than said lower flue.

8. In a furnace construction as defined in claim 7, wherein each saidbafile extends for about 360.

9. In a furnace construction as defined in claim 8, wherein said firstplurality of bafiles slope in the same direction as said secondplurality of bafiles.

10. In a furnace construction as defined in claim 8, wherein said firstplurality of baflles slope in the opposite direction to said secondplurality of bailles.

11. In a furnace construction having a generally cylindrical combustionchamber disposed with its longitudinal axis in vertical position, spacedwalls defining an annular enclosure including an inner wall of greaterdiameter and disposed substantially coaxially with and in spaced lateralrelation to said combustion chamber, means for conveying hot gases fromsaid combustion chamber to said annular enclosure, a tubular exhaustflue extending outwardly for leading said gases from the upper portionof said annular enclosure, a shell surrounding said annular enclosure inspaced relation to the outer wall thereof, and blower means foreffecting passage of air to be heated through the space between saidcombustion chamber and annular enclosure and also through the spacebetween said annular enclosure and shell, the improvement whichcomprises two vertically aligned tubular flues connecting saidcombustion chamber with said annular enclosure, said connecting fluesbeing disposed opposite said exhaust flue and one of said connectingflues being smaller in diameter than the other said connecting flue withthe 3 smaller flue connecting with the upper portion of said annularenclosure and the larger flue connecting with the lower portion of saidannular enclosure; a first set of five equally spaced and equallyinclined spirally extending baffles between of said annular enclosureand said shell, said secnd set of bafiles extending spirally in the samedirection as said first set of bafiles and each of said second set ofbaiiles extending spirally for approximately 360 around said annularenclosure, and one of said second set of bailles intercepting saidexhaust flue substantially centrally of said exhaust flue, all of saidbafiles being adapted to cause air to be heated to follow a plurality ofcircuitous paths in passing through said spaces.

12. In a furnace construction having a generally cylindrical combustionchamber disposed with its longitudinal axis in vertical position, spacedwalls defining an annular enclosure including an inner wall of greaterdiameter and disposed substantially coaxially with and in spaced lateralrelation to said combustion chamber, means for conveying hot gases fromsaid combustion chamber to said annular enclosure, a tubular exhaustflue extending outwardly for leading said gases from the upper portionof said annular enclosure, a shell surrounding said annular enclosure inspaced relation to the outer wall thereof, and blower means foreffecting passage of air to be heated through the space between saidcombustion chamber and annular enclosure and also through the spacebetween said annular enclosure and shell, the improvement whichcomprises two vertically aligned tubular flues connecting saidcombustion chamber with said annular enclosure, said connecting fiuesbeing disposed opposite said exhaust flue and one of said connectingfiues being smaller in diameter than the other said connecting flue withthe smaller flue connecting with the upper portion of said annularenclosure and the larger flue connecting with the lower portion of saidannular enclosure; a first set of four equally spaced and equallyinclined spirally extending baffles between said combustion cham her andthe inner wall of said annular enclosure, each said bafile extending forapproximately 360* around said annular enclosure, one of said first setof bafiles intercepting said upper flue centrally of said flue andanother of said first set of bafiles intercepting said lower fluecentrally of said flue; and a second set of four equall spaced andequally inclined spirally extending bafiies between the outer wall ofsaid annular enclosure and said shell, said second set of bailles extending spirally in the opposite direction to said first set of baiiles andeach of said second set of baliles extending spirally for approximately360 around said annular enclosure, and one of said second set of baiilesintercepting said exhaust flue substantially centrally of said exhaustflue, all of said baffles being adapted to cause air to be heated tofollow a plurality of circuitous paths in passing through said spaces.

13. In a furnace construction having a combustion chamber disposed withone axis thereof in generally vertical position, spaced walls definingan enclosure disposed in spaced relation to and surrounding saidcombustion chamber, and including an inner wall disposed in spacedlateral relation to said combustion chamber, means for conveying hotgases from said combustion chamber to said enclosure, means forpermitting said gases to exhaust from said enclosure, a shellsurrounding said enclosure in spaced relation to the outer wall thereof,said shell and outer wall defining an air passage and said combustionchamber and inner wall defining another air passage, and means foreffecting movement of air to be heated through said passages, theimprovement which comprises a first plurality of generally spirallyextending battles between said combustion chamber and said enclosureinner wall; and a second plurality of generally spirally extendingbaflies between said shell and said enclosure outer wall.

RAY W. RIFLEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 11,278 Sweeney July 11, 1854251,320 Towne Dec. 20, 1881 309,495 McCreary Dec. 16, 1884 446,222 HoytFeb. 10, 1891 563,240 McCowatt June 30, 1896 1,606,494 Barnhart Nov. 9,1926 1,811,182 Neal June 23, 1931

